Define biological membrane?

Hint: Biological membrane function as the barriers or the gatekeepers. They permit only a few molecules to pass through them and restrict the others as they are semi-permeable or selectively permeable in nature.

Complete Answer:
Biological membranes are the barriers which separate the cells or the organelles from the outside or surrounding and form intracellular compartments. It is a phospholipid bilayer which is formed by the aggregation of the lipids in aqueous solution. The hydrogen bond between the lipids helps to aggregate the layer.

Composition of the biological membrane- It is made up of:
1. Lipids: The membrane is a bilayer of lipids which has hydrophilic head and hydrophobic tail. It is not continuous due to the presence of other molecules like proteins, carbohydrates.
2. Proteins: The membrane consists of different proteins which play vital roles in the physiological process. The membrane proteins consist of the enzymes which catalyze different reactions, carrier proteins which help in transport of molecules to and fro the membrane, integrins which contain actin filaments helps in maintaining the integrity of the cell.
3. Oligosaccharide: The oligosaccharides are the polymers of carbohydrates with binds to the lipid and proteins. They help in cell adhesion due to the formation of hydrogen bonds.

Note: The important function of the biological membrane is it is selectively permeable in nature. It allows the entry and exit of the biomolecules. This is carried out by the help of sodium/potassium pump. It provides rigidity and shape to the cell and the organelles. The composition of the biological membrane differs from cell to cell and organelle to organelle depending on the function and the type of biomolecules that are moving in and out.